I think it sounds cool too, but I think the potential ecological impacts could be huge, all sorts of living things are adapted to tress the way they are now, A sudden proliferation of trees that glow in the dark would be a game changer for insects other plants, birds, bats you name it. I don't even particularly consider myself an environmentalist, and I'm in favor of GM food crops, but I think I would want to see some serious impact studies on this before we start lining the streets with glowing trees.

Sadly, I think you are absolutely right. It would be so nice just to run w/ this, maybe just in towns would be ok? And if they are sterile too maybe not such a big deal since cities are already all lite up anyways?

Good point - genetically engineered crops have already been proven to pass their genes into neighbors crops by pollen drifting in the wind. The big ag companies sue the unfortunate recipients for patent infringement, even though they did not want the genes and did nothing to get them - it was all passive. Genetically engineered grass has 'escaped' field trials in Oregon or Idaho (I forget which). Add to that, trees like Norway Maples have displaced native trees in some forests, and are considered 'weeds'. Glow-in-the-dark trees would be really interesting and cool, but we wouldn't want them causing more harm than good.

I suspect they would be less 'fit' from an evolution point of view - the energy that they require to produce light would take away from growth and reproduction. Similar to variegated plants, that have areas of white or yellow replacing their photosynthetic green areas - they often mutate back to green and then they grow much better.